1. Field of the Invention
This invention relates to an apparatus for automatically switching connections of conduit pipes of a liquid treating plant useful in various manufacturing processes in the fields of foods, pharmaceutics, cosmetics, chemicals or the like.
2. Description of the Prior Art
In a liquid treating plant for food or chemical products, for example, there often arises a necessity for periodically cleaning and sterilizing a number of conduit pipes with a cleaning liquid or steam which is supplied thereto through a multiple-point conduit switching apparatus.
As regards the conduit switching apparatus which serves for this purpose, there are known technologies as described, for instance, in Japanese Patent Publications 46-35309 and 50-1089. The conduit switching apparatus of these prior art publications are generally constituted by a fixed plate having switch ports on its surface in communication with a plural number of conduit pipes, a movable member with a number of U-shaped switch pipes having open ends thereof disposed in face to face relation with the ports in the fixed plate, and a drive mechanism adapted to drive the movable member for linear reciprocating movements and rotational or angular rocking movements relative to the fixed plate, switching connections of the conduit pipes by combination of the linear reciprocating movements and the rotational rocking movements of the movable member relative to the fixed plate.
A problem with the conduit switching operations is that liquid leaks take place at the conduit switch points where the switch ports of the conduit pipes are selectively connected by the switch pipes, necessitating to wash the switch points with a cleaning liquid, which however scatters around and tends to cause troubles to the drive mechanism and controlling electrical wiring for the movable member as well as to support structures of the movable member and various metering instruments, making it extremely difficult to perform the multiple-point conduit switching operations under centralized control from a remote place. On the other hand, especially in case of a liquid treating plant for a food or chemical product, the washing operation relying on human manual labor is undesirable from the Viewpoint of sanitariness and contamination with microorganisms.
In this regard, the afore-mentioned Japanese Patent Publication 46-35309 proposes to use, for washing the conduit switch points, a sprayer located over a cover which encloses the switch points. However, a sprayer of this sort fails to clean the switch points of conduits to a sufficient degree, in addition to a problem that the washing operation is time-consuming.
Further, a number of problems have to be solved before realization of automatic conduit switching operation. For example, when the switching ports of conduit pipes are opened for the switching operation, the seal packings which are provided at the switching points often fall off, and this trouble is conspicuous especially in case of conduits which convey a highly viscous liquid or which have a high internal pressure. Manually remounting the fallen-off packings is not only troublesome but also undesirable in a liquid treating plant of food or pharmaceutical products in view of the possibilities of secondary contamination with microorganisms of the liquid under treatment through contact with human body.
The liquid leaks from the switch points of the conduit pipes also take place as a result of damages to or ageing of the seals or packings at the switch points.
Such liquid leakage at the switch points has to be detected promptly in case of a liquid treating plant for food or pharmaceutical product to preclude the possibilities of the secondary contamination with microorganism. Further, when the movable member proceeds to a next action prematurely for some reason without completing a predetermined stroke, this has to be detected promptly in a reliable manner.